1. Field of the Invention
The present invention relates to a tool suspension device, and more particularly to a tool suspension device has a separatable tool bracket with offset parting lines, and a plastic injection mold assembly for making the tool bracket.
2. Description of Related Art
With reference to FIG. 9, a conventional tool suspension device in accordance with prior art comprises a suspension board (50), a tool bracket (51) and fasteners (52). The suspension board (50) has a front (not numbered) and a bottom (not numbered). The tool bracket (51) is mounted detachably on the front of the suspension board (50) at the bottom and comprises a U-shaped body (not numbered) and two mounting feet (not numbered). The body has a longitudinal tool slot (511), a front (not numbered) and two opposite sides (not numbered). The mounting feet are formed respectively on and protrude respectively from the sides of the body. The fasteners (52) are attached respectively to the mounting feet to fasten the tool bracket (51) on the front of the suspension board (50). Therefore, a tool, such as a wrench (70) can be inserted into and held in the tool slot (511) for suspension.
Both the suspension board (50) and tool bracket (51) are made by plastic injection molding. The suspension board (50) and tool bracket (51) need separate mold sets. For custom specialty products, the front of the body of the tool bracket (51) is molded with a product indicator (512), such as trademarks, significant symbols, characters, etc. to provide relevant product information about the tool suspension device.
With reference to FIGS. 9 and 10, a plastic injection mold assembly (not numbered) in accordance with the prior art to make the tool bracket (51) with the front product indicator (512) is mounted on a mold base (60) and comprises a lower part (61) and an upper part (62). The lower part (61) is mounted on the mold base (60) and has a top (not numbered) and multiple cores (611) formed on the top. The cores (611) are arranged along two straight lines.
The upper part (62) is mounted detachably on the top of the lower part (61) and comprises a common mold (620) and two interchangeable molds (622). The common mold (620) has a top (not numbered), a bottom (not numbered), two channels (not numbered) and multiple cavities (621). The cavities (621) are defined in the bottom of the common mold (620) and correspond respectively to the cores (611). Each pair of corresponding cavity (621) and core (611) fabricates a tool bracket (51). The channels are defined in the top of the common mold (620) and are aligned respectively with the in-line cavities (621). Each of the cavities (621) has a bottom (not numbered), a molding surface (not numbered) and an opening (not numbered). The molding surface is used to shape the body of the tool bracket (51). The opening is defined through the bottom so that the cavities (621) communicate respectively with the channels.
The interchangeable molds (622) are mounted respectively in the channels and have multiple bottom protrusions (not numbered). The bottom protrusions are respectively fitted and held in the openings of the cavities (621) and have respectively a parting surface (not numbered) flush with the bottom of the adjacent cavity (621). To make the product indicator (512) such as a string of Arabic numerals on the front of the body of the tool bracket (51) (e.g. 2004 shown in FIG. 9), each parting surface has a marking portion (624) to mold the product indicator (512) on the front of the body of the tool bracket (51). The marking portion (624) may be indentations to form a solid product indicator (512) or protrusions to form an indented product indicator (512).
Therefore, when the contents of the product indicator (512) needs to be changed, only the interchangeable mold (622) has to be replaced with a new one, which will save cost of the mold assembly.
However, the described mold assembly causes a parting line (53) around the product indicator (512) on the front of the body of the tool bracket (51). The parting line (53) is formed during the injection molding along the interface of the opening in the bottom of each cavity (621). Improper location of the parting line (53) on the front of the body of the tool bracket (51) will effect the appearance of the tool bracket (51) and cause the front of the tool bracket (51) to be untidy. Therefore, the whole tool suspension device becomes unsightly.
In addition, defining the opening in the bottom of each of the cavities (621) forms an annular protrusion (623) that protrudes into the molding surface of the cavity (621). The annular protrusions (623) will restrict machining means for defining the cavities (621) in the common mold (620). Electric discharge machining (EDM) is the only way to define the cavities (621) except wire-cut electric discharge machining. Wire-cut machining cannot be used because of the annular protrusions (623). Electric discharge machining requires more time and cost to define the cavities (621) than wire cutting machining does.
To overcome the shortcomings, the present invention provides an improved plastic injection mold assembly to make a separatable tool bracket with offset parting lines to mitigate or obviate the aforementioned problems.